Correlation–polarization effects in electron/positron scattering from acetylene: A comparison of computational models

Different computational methods are employed to evaluate elastic (rotationally summed) integral and differential cross sections for low energy (below about 10 eV) positron scattering off gas-phase C2H2molecules. The computations are carried out at the static and static-pluspolarization levels for describing the interaction forces and the correlation–polarization contributions are found to be an essential component for the correct description of low-energy cross section behavior. The local model potentials derived from density functional theory (DFT) and from the distributed positron model (DPM) are found to produce very high-quality agreement with existing measurements. On the other hand, the less satisfactory agreement between the R-matrix (RM) results and measured data shows the effects of the slow convergence rate of configuration-interaction (CI) expansion methods with respect to the size of the CI-expansion. To contrast the positron scattering findings, results for electron–C2H2 integral and differential cross sections, calculated with both aDFTmodel potential and the Rmatrix method, are compared and analysed around the shape resonance energy region and found to produce better internal agreement. 2007 Elsevier B.V. All rights reserved. PACS: 31.25.v; 34.80.Bm; 34.85.+x